How to watch Great Conjunction 2020: Jupiter and Saturn 'double planet' on December 21

Jupiter and Saturn will seem as if they are merging in the night sky on Monday, appearing closer to one another than they have since Galileo’s time in the 17th century.

Astronomers say so-called conjunctions between the two largest planets in our solar system aren’t particularly rare.

Jupiter passes its neighbour Saturn in their respective laps around the sun every 20 years.

But the one coming up on Monday is especially close: Jupiter and Saturn will be just one-tenth of a degree apart from our perspective or about one-fifth the width of a full moon.

They should be easily visible around the world a little after sunset, weather permitting.

Saturn and Jupiter seen from Japan
Saturn and Jupiter (right) are converging ahead of their closest visible conjunction in 400 years. Credit: AP

Toss in the winter solstice in the northern hemisphere, the longest night of the year - and the summer solstice in the southern hemisphere - and this just-in-time-for-Christmas spectacle promises to be one of the greatest of Great Conjunctions.

It is also known as the “Christmas Star.”

Saturn and Jupiter set behind the Statue of Liberty on December 17, 2020 in New York City.
Saturn and Jupiter set behind the Statue of Liberty on December 17, 2020 in New York City. Credit: Gary Hershorn/Getty Images

“What is most rare is a close conjunction that occurs in our night-time sky,” said Vanderbilt University’s David Weintraub, an astronomy professor.

“I think it’s fair to say that such an event typically may occur just once in any one person’s lifetime, and I think ‘once in my lifetime’ is a pretty good test of whether something merits being labelled as rare or special.”

How to watch in Australia

In Australia, the conjunction will be best visible just after 8 pm WST or 11 pm AEDT on Monday, and there will be just a small window within which to view it.

“To see the conjunction no matter where you are in the world, you will need to go out in the early evening and if you’re in the Southern Hemisphere, you will need to look low in the West and Jupiter will be on the left and Saturn will be on the right at about the 4 o’clock position from Jupiter,” the Perth Observatory states on its website.

“A few days before the conjunction, on the 17th of December, the crescent moon will scrape past the two planets providing us with another conjunction for astrophotographers and stargazers to see.”

In Australia, the conjunction will be best visible just after 8 pm WST or 11 pm AEDT on Monday.
In Australia, the conjunction will be best visible just after 8 pm WST or 11 pm AEDT on Monday. Credit: buradaki/Getty Images/iStockphoto

Closest since 1623

It will be the closest Jupiter-Saturn pairing since July 1623, when the two planets appeared a little nearer.

This conjunction was almost impossible to see, however, because of its closeness to the sun.

Considerably closer and in plain view was the March 1226 conjunction of the two planets - when Genghis Khan was conquering Asia.

Monday’s conjunction will be the closest pairing that is visible since way back then.

Saturn and Jupiter have been drawing closer in the south-southwest sky for weeks.

Jupiter - bigger and closer to earth - is vastly brighter.

“I love watching them come closer and closer to each other and the fact that I can see it with my naked eyes from my back porch,” Virginia Tech astronomer Nahum Arav said in an email.

Despite appearances, Jupiter and Saturn will actually be more than 730 million km apart.

Earth, meanwhile, will be 890 million km from Jupiter.

A telescope will not only capture Jupiter and Saturn in the same field of view, but even some of their brightest moons.

Their next super-close pairing will occur on March 15, 2080.






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